Enterprise storage systems are increasingly hard to manage. Today's high-end storage arrays are complex and highly configurable, and therefore inherently difficult to reason about. Furthermore the trend toward storage consolidation in large data centers means that a single “black box” storage array can serve a variety of very different workloads. The mapping from fundamental device capabilities, configuration, and workload to performance often defies manual analysis by human experts, and researchers have therefore begun to automate tasks such as capacity planning and configuration. This approach centralizes performance modeling, but the construction of performance models remains challenging. State-of-the-art approaches rely heavily on expert analysis, but it is difficult for human analysts to keep pace with increasingly elaborate and often proprietary enterprise storage architectures. Enterprise storage trends call for modeling strategies that are more automated, less reliant on human expertise, and applicable to opaque devices.
A storage array is a complex device that typically includes a collection of disks, a controller, and one or more caches. An enterprise storage array is a more complex device that typically includes a plurality of groups of independent disks, a read cache for each group of independent disks, a controller, a non-volatile cache for write data, a high-speed internal interconnect architecture, and several client host interface processors for receiving and responding to storage requests.
Existing methods for storage system performance modeling are not suited to forecasting response times of individual requests for storage arrays and, in particular, for enterprise storage arrays. Analytic models predict average performance (e.g., mean throughput, mean response time) from parametric workload descriptions (e.g., mean request rate, read:write ratio). Simulation models can generate storage request response time predictions but require calibration and a tool for performing the calibrations is available only for disk drives; nothing analogous exists for storage arrays and, in particular, for enterprise storage arrays.